In a recent interview, Twitter CEO Dick Costolo noted that sign-ups for the social network have increased by three times since Apple’s Twitter integration feature (in iOS 5) went public. He also noted that over 250 million tweets are being published each day, meaning Twitter is serving one billion tweets every four to five days.

Costolo said:

The iOS integration is going to be absolutely huge for us, even better than we thought it was. I didn’t realize how frictionless this would be. It’s so native.

The feature allows users to sign-in to their Twitter account via the Settings app, and publish photos, video and more to the micro-blogging social network.

"Create New Account"

Importantly, it’s also possible to sign-up for a Twitter account from within the Settings app in iOS 5.

Clearly, integrating Twitter within Apple’s mobile operating system not only makes interacting with the social network easier for iOS users, but it also has the capacity to massively increase interest in the social network itself, as Costolo’s comments evidence. As more Apple fans download iOS 5 or purchase iOS 5 equipped mobile devices, more iOS users are going to sign-up for the service, or at least sign-in to it and contribute towards those 250 million tweets a day.

Have you been taking advantage of Twitter integration in iOS 5? Let us know in the comments.